brake booster bracket

[80CJ6]

I am doing a rear disc/power brake upgrade on a 78CJ5. I have stockpiled Lincoln Mark VII calipers, newer 7/8 CJ front discs, 8" dual diaphragm booster, corvette type disc/disc 1" master cylinder, disc/disc proportioning valve, and all flex lines are braided stainless. I've read everything I could find on doing the swap but I get conflicting opinions about using the brake booster brake. Some say mount booster directly to firewall, others say the bracket is a must have. I am running a small block stroker with outside the frame Hooker headers which come over top of the steering column so I would prefer not to extend the booster/MC any further forward than necessary. Any suggestions/opinions would be greatly appreciated!!

 

[JR74CJ5]

Moved this over to the right spot for you You should (hopefully) get some faster answers here!

(I'm not very knowledgeable on this subject myself...)



~ Jr

 

[80CJ6]

Thanks. I think the reason that CJs used the bracket with the fulcrum was to lower the booster so it would clear the hood. I found a YJ bracket which is straight with no offset. I think it will move the booster away from the firewall enough to clear the hood reinforcement where the hinges bolt on. For $5 its worth a shot. Will have to have an extended pushrod though. Thanks again for moving my post to where I might get a response. Was starting to wonder how friendly folks were.

 

[JR74CJ5]

Theres a great bunch of good guys on here... I would expect by tonight you'll have a few of them on here with ya.

 

[tarry99]

I am doing a rear disc/power brake upgrade on a 78CJ5. I have stockpiled Lincoln Mark VII calipers, newer 7/8 CJ front discs, 8" dual diaphragm booster, corvette type disc/disc 1" master cylinder, disc/disc proportioning valve, and all flex lines are braided stainless. I've read everything I could find on doing the swap but I get conflicting opinions about using the brake booster brake. Some say mount booster directly to firewall, others say the bracket is a must have. I am running a small block stroker with outside the frame Hooker headers which come over top of the steering column so I would prefer not to extend the booster/MC any further forward than necessary. Any suggestions/opinions would be greatly appreciated!!

The bracket does several things, First it moves the Booster away from the firewall if you have a clearance issue.........on Jeeps with a hydraulic Clutch the Clutch MC is tucked in behind and next to the extension bracket to line up with the swing pedals. The linkage in that bracket and its offset can also effectively change your pedal ratio too.

If you don't need it don't use it. But if your coming from manual brakes your pedal ratio for Power will be off ( 3-4:1 for power and 6-7:1 for manual) you have to mount the Booster in the correct location so that the pushrod correctly lines up with the correct position on your brake pedal........keep in mind your working in reverse now since your pedals are already mounted, so correct location of the Booster / MC will dictate what your pedal ratio will be...............lots of things to pay attention to in order to get everything working properly.............here's a link.....it goes over a lot of things I mention here and more...........read it.
Pirate4x4.Com - The largest off roading and 4x4 website in the world.

 

[80CJ6]

Thanks99. I saw your post just before bed. I took a quick glance at the link you provided. I had used the formulas in Allen's Jeep performance handbook to calculate the bore of the master cylinder I would need but it looks like I have many more factors to consider for a balanced rig, pedal ratio being near the top of the list. I have seen something about lowering the pedal ratio in other site postings but was never clear about how that could be accomplished. I have been gathering all my parts to get ready to do the conversion but it looks like I have a lot more studying before I jump in. Tanks again for the info.

 

[tarry99]

Thanks99. I saw your post just before bed. I took a quick glance at the link you provided. I had used the formulas in Allen's Jeep performance handbook to calculate the bore of the master cylinder I would need but it looks like I have many more factors to consider for a balanced rig, pedal ratio being near the top of the list. I have seen something about lowering the pedal ratio in other site postings but was never clear about how that could be accomplished. I have been gathering all my parts to get ready to do the conversion but it looks like I have a lot more studying before I jump in. Tanks again for the info.

80CJ6,

I'm glad your taking the time to read and understand all the important factors required to make a good Brake system. Understanding them and then applying the principles can be to different animals in any vehicle , at which point we all have to compromise something...........the good news is you will understand the compromise.

Lowering the pedal ratio simply means lowering or taking away some of the mechanical advantage at the pedal.........your swing pedals have a center shaft that both the brake and the clutch pedals swing on..........measure from that point down to where your foot contacts the pedal. The top point is called your fulcrum point.........measuring down from that point to the pick up or push point for the brake to MC push rod will establish the ratio once both dimensions are divided into each other.

If your using a non power brake set of swing pedals that have a higher mechanical advantage on a new power brake system the brakes will be "touchy" to the point of being hard to drive /top.